1. Field of the Invention
The present general inventive concept is directed to a method and apparatus, and directed to a main stage cartridge.
2. Description of the Related Art
One trend in modern hydraulics is towards higher operating pressures in order to provide more work with a smaller actuator. There is also a desire to minimize energy consumption.
Currently, there is widespread use of hydraulic cartridge valve technology. Hydraulic cartridge valves do have high insertion losses due to small fluid passages coupled with multiple fluid directional changes
Hydraulic cartridge valves in present use are either of screw-in or slip-in construction. Screw-in cartridges are threaded into a cavity. The torque required to pre-load the cartridge in its cavity can be substantial in a larger valve. For example, a screw-in cartridge valve rated for a nominal flow of 200 gpm can have a pre-load torque requirement of 375 foot-pounds.
Slip-in cartridge valves, known as 2/2 valves or logic valves, are generally held in a cavity by a cover plate retained with socket head cap screws. The pre-load torques are much lower for a given nominal flow size. Most are designed to be used within cavities defined by standards DIN 24342 and ISO 7368.
For both screw-in and slip-in cartridge valves, the typical axis of fluid discharge is offset 90 degrees from the axis of fluid inlet.
Hydraulic cartridge valves currently utilize either a poppet or spool construction. Spool type hydraulic valves have disadvantages at higher pressures due to leakage between the valve sleeve and spool. Close fits are desired to minimize (but not eliminate) leakage. Despite this leakage may be unacceptably high as system working pressures increase. This results in wasted energy and heat as high-pressure hydraulic fluid is discharged to lower pressure without doing any useful work.
Silting is also a problem. Spool valves are vulnerable to fine fluid contamination. Debris deposited between the spool and the sleeve may result in erratic valve shifting, or the valve not shifting at all. Continuous leakage is present in spool type valves, even when the valve is closed, representing a continuous loss of energy.
Therefore, what is needed is a cartridge valve that can improve upon the deficiencies of the prior art.